Impervious barrier comprising polyolefin fabric, asphalt and asbestos

ABSTRACT

An impervious cover structure is produced by laying a polyolefin fabric fused on one side only, fused side against the surface to be covered and the unfused side is coated with a mixture containing asphalt and asbestos fibers.

Bresson et al.

Feb. 4, 1975 IMPERVIOUS BARRIER COMPRISING POLYOLEFIN FABRIC, ASPHALTAND ASBESTOS Inventors: Clarence R. Bresson; Forrest D.

Assignee:

Filed:

Spaulding, both'of Bartlesville, Okla.

Phillips Petroleum Company, Bartlesville, Okla.

Dec. 14, 1971 Appl. No.: 207,800

[56] References Cited UNITED STATES PATENTS 2,733,159 1/1956 Scoggin etal. 106/282 3,474,625 10/1969 Draper et a1 161/92 3,505,260 4/1970Woodruff 260/285 A 3,719,546 3/1973 Parlin 161/154 3,729,373 4/1973Hildebrandt et a1 161/205 Primary Examiner-William J. Van BalenAssistant Examiner-James J. Bell [57] ABSTRACT U Q Cl 117/138 8 El06/282 7/168 An impervious cover structure is produced by laying a 'gi''i' m 161/170 161/205 polyolefin fabric fused on one side only, fusedside ln t. CL... 1332b 27/00 surface be Field of Search 161/81,82,151,154,155, 161/156, 164, 170, 205; 156/148; 117/138.8

is coated with a mixture containing asphalt and ashestos fibers.

E, 168; 106/282 2 Claims, 1 Drawing Figure 2 COATS CATIONIC ASPHALTEMULSION CONTAINING 65% SOLIDS 1.7 LBS/SQ YD AT 22 FT DEPTH (10 P816) 2coATs CUTBACK AIR-BLOWN ASPHALT 2.0 LBS/SQ YD AT 67 FT DEPTH (3o Pslc) 2COATS CUTBACK AIR-BLOWN ASPHALT WITH 5% ASBESTOS ONLY IN 2ND COAT 4.0LBS/SQ YD AT 67 FT. 7 DAY AIR CURE l COAT CUTBACK AIR-BLOWN ASPHALT WITH5% ASBESTOS 3.8 LBS/SQ YD AT 6'! F116 DAY AIR CURL 2 COATS CUTHACKAIR-BLOWN ASPHALT WITH 5 9f, ASBESTOS ONLY IN 2ND COAT 3.0 LBS/SQ YD AT67 FT. FINAL CURE BHRS A1140 F IN AIR CIRCULATING OVEN l 1 l I 3o 40 50so T I ME (HOURS) 1 COAT CUTBACK AIR-BLOWN ASPHALT WITH 5% ASBESTOS 4.2LBS/SQ YD AT 67 FT. FINAL CURE 12 HRS AT 140F IN AIR CIRCULATING OVEN(I) INDICATES NO FAILURE (TEST TERMINATED) 12) ALL sAMPLEs WERE ON 502/361 YD FABRIC I3) SIMULATED DEPTH BY APPLIED PRESSURE IN A TESTAPPARATUS IMPERVIOUS BARRIER COMPRISING POLYOLEFIN FABRIC, ASPHALT ANDASBESTOS This invention relates to an impervious cover structure. ln oneof its aspects, it relates to a cover structure comprising a polyolefinfabric, asphalt and asbestos fibers. in another of its aspects, theinvention comprises a surface or object to which has been applied animpervious cover structure comprising a polyolefin, for example, anon-woven polyolefin fabric, mat, or web, the polyolefin beingimpregnated with a mixture containing asphalt and asbestos fibers. Italso relates to a method for producing covers or coatings as describedherein. Further, in a specific aspect, the invention relates to areservoir or pond or other container which is rendered fluid retentiveby applying thereto an impervious cover structure according to theinvention.

In one of its concepts the invention provides a cover structure which isproduced by fusing externally on one side, or at least on one side, apolyolefin fabric, mat, or web, laying said fabric, mat, or web with itsfused side against an object surface or ground to be rendered imperviousand then coating said fabric, mat, or web on a provided unfused externalside with a mixture containing asphalt and asbestos fibers.

In another of its concepts the invention provides a reservoir, containeror pond having a liner or structure applied to the surface thereof asherein described.

Various liners have been provided for covering objects or surfaces orthe ground to render these impervious to fluids, for example, to water,or other liquids. In places at which the fluid or liquid exertsconsiderable pressure against the covering structure or liner, leakageis often observed. The leakage occurs at so-called pin hole openings inthe coating or covering structure. These leaks have been observed,particularly with nonwoven fabrics which have been coated with varioussealants. Thus, in fairly deep pond liner applications, it has beenobserved that asphalt sealed non-woven polypropylene fabric can developpin hole leaks which may be due to cold flow.

We have now conceived of an improved cover structure. Thus, we haveconceived that if the non-woven fabric is provided with a fused externalside and a nonfused external side, and is laid fused side against theobject to be covered or fused side down on the ground as in the liningof a pond and is then covered or coated with asphalt-containing asbestosfibers, as further described herein, the resulting structure will notdevelop leaks.

An object of the invention is to provide a cover structure. A furtherobject of the invention is to provide a fluid or liquid impervious coverstructure suitable for application to objects to be protected againstfluid or liquid. A further object of the invention is to provide a linerfor liquid storage ponds. A still further object of the invention is toprovide a cover structure of improved character in that it willwithstand liquid pressure of considerable magnitude, yet not developleaks. A further object of the invention is to provide a cover structurecomprising a non-woven fabric covered with asphalt which will not flow,once cured, clue to cold flow through windows in the non-woven fabric.

Other aspects, concepts, objects and the several advantages of theinvention are apparent from this disclosure and the appended claims.

According to the invention, there is provided an impervious coverstructure which comprises a non-woven polyolefin fabric, mat, or web,fused externally on one side and having unfused fiber on the otherexternal side thereof, the fused side being laid against the material tobe covered, the unfused fibrous side being coated with a mixturecontaining asphalt and asbestos fibers.

The asphalt-asbestos mixture which is applied is usually applied as acut-back asphalt. The cut-back asphalt is prepared from an air-blownasphaltic material having a penetration of about 20-50, preferably25-35, a minimum ductility at 77 F of 5, and a Ring and Ball softeningtemperature of l60-l75 F.

The cut-back solvent used to prepare the cut-back asphalt is selectedfrom kerosene, cycle oil, Stoddard solvent or, in general a hydrocarbonbased material having an initial boiling point in the range of l60-450F, preferably 200-300 F.

Sufficient cut-back oil is used to make the resultant blend applicableto the surface by hot application not exceeding about 250 F (meltingpoint of polypropylene) at a temperature which will not adversely meltthe fabric or by spray or brush technique at ambient temperatures.Usually about 20-100 parts by weight of solvent, preferably about 40-70parts by weight per 100 parts by weight of asphaltic material, are used.

The asbestos fiber is added to the cut-back asphalt in amounts fromabout 4-10 parts/100 parts by weight of cut-back asphalt. It can have afiber length of about 0.0l-0.l in., preferably about 0.03-0.06 in. Whilethe presence of longer fibers can be tolerated, the preferred range ismore readily handled by the usual equipment and best improves thedesirable properties of the asphalt, such as the penetration values.

It has been found that using an approximately 4 oz- /yd fabric, anasbestos fiber content of about 6-8, or more, parts/100 parts ofcut-back asphalt is preferred, while for a 5 02. web a fiber content ofabout 5-6 in the cut-back asphalt is sufficient.

The fabric is made from about 2-20 denier, preferably about 3-8 deniercrimped staple about one-half to about 3 in. long; a batt of thesefibers is needle punched by conventional means and the needle punchedfabric is then passed through a pair of nip rolls, one of which isheated above the melting point of the fibers to heatfuse the fibers onone side. The amount of fusion is adjusted to give the final product atensile strength of from about 10 lbs. to about lbs/inch of width, thestrength depending both on the amount of fusion, weight of fabric anddenier of the fiber. The fabric is about 1-5 mm thick under nocompression and ordinarily less than about 10% of the thickness of thefabric is fused.

The polypropylene fabric should have a weight of at least about 3.5-4ox/yd and is fused on one side only. A heavier fabric weighing about 5-6ox/yd is now preferred. Much heavier fabrics become uneconomical andheavy to handle.

A capped product, i.e., a light fabric fused on both sides, having a capof [-2 oz/yd of additional fiber, e.g., nylon, attached to one sidethereof by an added needle punch operation and having a total weightbetween about 4.0 and about 5.5 oz/sq yard is also suitable. The addedfiber now acts as does the unfused side of the fabric which is fused onone side only. Thus, the capped side is the one to which the cut-backasphalt/asbestos mixture is applied.

It is obvious that there are a number of variables which coact toprovide an effective leak-proof liner. Under mild conditions, forexample, a shallow, sweet water pit or ditch, an asphalt with higherpenetration can be used and a more fluid cutback formulation containingless asbestos can be used. For more severe conditions, deep water, hightemperature and brine, for example, a lower penetration asphalt is usedwith a heavier mat and more asbestos; this more viscous material mayhave to be applied hot (v.s.). These and other variables can bedetermined by mere routine testing by one skilled in the art inpossession of this disclosure.

It is essential, however, that the asbestos fibers in the mixture beforced by the flow of the liquid through the mat into immediate contactwith the surface of the mat where they become imbedded in theunconsolidated top surface of the fabric and lodge in the interstitialvoids present therein.

The bar graphs reflect results obtained without and by using theinvention. These are comparable.

Referring now to the bar graph, these indicate by their lengths the timein hours at certain pressures required for failure of the coverstructure indicated.

The pressure was applied in a test apparatus into which water was fedand maintained under pressure against the test covered structuresupported on a screen.

There are six tests shown in the bar graph. Failure or end of test withfailure is indicated by the bars which have smooth or straight lineendings. The cut-away endings in tests 4 and 6 indicate that the testswere still under way at the indicated time in hours.

The final oven cure for tests 5 and 6 was for 8 and 12 hours at 140 F inan air circulating oven, respectively.

It can be seen that one coat covering with cut-back asphalt containingasbestos according to the invention yields results which are farsuperior to those obtained even with two coats of covering when theasbestos is only in the second coat. Thus, the tests demonstrate acoaction between the asbestos in the asphalt and the fabric to which itis applied.

It will be evident to one skilled in the art in possession of thisdisclosure and having studied the same that there must needs be,according to the invention, loose or unfused fibers on the externalsurface of the fabric to which the asphalt-asbestos mixture is applied.Thus, it is within the scope of the invention to use a fabric which hasbeen fused on both sides but to which there has been applied additionalfiber in some manner or other as by a needle punch operation.

The asbestos fiber now preferred is Johns-Manville 7MO2 fibers. Theseasbestos fibers were used in the specific tests reported in the bargraphs. The fabric used was a non-woven polypropylene five ounce persquare yard fabric, heat-fused on one side. This fabric is nowpreferred. The mixture of asphalt-asbestos and solvent should be readilysprayable at temperature of ll 80 F. and as such can be applied tovertical surfaces as well as horizontal ones. Applications in additionto those described are various. Various shaped objects in addition toponds can be covered. Inside of tanks of various shapes can be covered.Rooftops, especially those which may be structured to accumulate and toretain liquid as a shield against heat can also be covered. Indeed,though the structure of the invention is particularly well suited foruse under considerable hydrostatic pressure, it can, of course, be usedin all those places where fabric reinforced asphalt containing coveringsare used.

The following examples include data from which the bar graph has beenprepared, as well as other data.

EXAMPLE 1 Polypropylene fibers of staple length, about 6 denier, werecarded and needle-punched to a consolidated fibrous bat. The bat wassubjected to a heating step in which it was passed through a pair of niprolls, one of which is heated to about 400 F to fuse the fibers on thatside. The resulting nonwoven fabric has a weight of about 5 oz/yd and anaverage thickness of about 2 PREPARATION OF CUT-BACK ASPHALT/ASBESTOSMIX The cut-back asphalt was prepared from an air blown asphalticmaterial having a penetration of 35, a ductility of 77 F of5 and a Ringand Ball softening temperature of 165 F. The asphalt was cut back withnaphtha, boiling range 200400 F, at a ratio of 100 parts of asphalt and50 parts of naptha. To this blend were added asbestos fibers with anaverage fiber length of about 0.05 in. Sufficient fibers were added toprovide about 5 parts by weight asbestos fibers in 100 parts of cutbackasphalt.

TEST PROCEDURE A sample of the non-woven fabric (5 oz/sq yd) wasspray-coated with the cut-back asphalt containing 5 percent asbestosfibers at a rate of two-thirds gal/yd and allowed to cure for 12 hoursat 140 F in a hot air oven. The fabric had no pin holes and was aneffective hydraulic barrier at 67 ft. at 80 F. The test was carried outin a static load apparatus in which a sample fabric is subjected to astatic hydraulic load at a controlled temperature and the time measuredto develop a leak. This sample was tested for 60 hours without failurewhen the test was discontinued.

EXAMPLES II V Other samples of 5 oz/yd fabric were variously treated andtested as in Example I.

1. Single coats of a cationic asphalt emulsion were applied on 2consecutive days and then allowed to cure in air at ambient temperaturefor 1 week. The sample failed under 10 psi load after about 6 minutes.

2. Two coats of air-blown. cut-back asphalt (2.0 lbs. asphalt/sq yd)without asbestos fibers on fabric samples were tested at 30 psi (67 ft)and failed after 60 minutes.

3. Two coats of air-blown cut-back asphalt were applied, the first coatwithout asbestos fibers and after a l-day cure the second coatcontaining 5 parts asbestos fibers/ parts of cut-back asphalt (4.0 lbsasphalt/sq yd). This sample failed after 45 minutes (7-day air cure).

4. One coat air-blown cut-back asphalt with 5 parts asbestos fibers/I00parts cut back asphalt (3.08 lbs/sq yd), 7-day air cure. The sample didnot fail after 22 hours at 30 psi (67 ft) when test was terminated.

EXAMPLE VI Samples of 4 oz non-woven fabric fused on one side werecoated with a cut-back asphalt containing 5 and 7 parts by weight ofasbestos fibers per 100 parts of cutback asphalt, respectively, curedand tested as before. The 4 oz material coated with the 5/100 mixturefailed after 5 hours while with the 7/100 mixture the test wasdiscontinued at 95 hours without failure.

EXAMPLE VI] A non-woven fabric was prepared by carding andneedle-punching 6 denier polypropylene staple and the about l /2 oz/sqyd nylon 66 staple was needle-punched into the bat and the polypropyleneside was fused. This nylon capped fabric had an approximate weight of 5/2 oz/sq yd.

A sample of this material was coated with two-thirds gal/sq yd of 5/100asbestos cut-back asphalt mixture and allowed to cure for 8 days. Underhydraulic test at 80 F and 30 psi (67 ft) no failure occurred after 130hours when the test was discontinued.

EXAMPLE Vlll A similar capped coated fabric was prepared, except that 6denier polypropylene fiber was substituted for the nylon of Example Vll.One coat of 5/l00 asbestos- /asphalt (one'half gal/sq yd) mix wasapplied as in Example Vll and the cured fabric was tested at 80 F and 30psi (67 ft). No failure had occurred after hours when the test wasdiscontinued.

It is evident from Example I that the spray coated fabric which had beencured was free from pin holes and was an effective barrier againsthydraulic pressure for a period of 60 hours.

In Examples ll V, it is shown that (l single coating asphalt emulsionapplied on 2 consecutive days or (2) single coats of cut-back asphaltapplied on 2 consecutive days, failed to provide an effective barrierunder comparative conditions. Also application ofa first coat (3)without and a second coat with asbestos fibers likewise failed toprovide a suitable barrier. A single coating including asbestos fibers(4) provided such a barrier.

Examples VII and Vlll show the use of a capped fabric, that is, a fabricwhich has a coating of, say, nylon or polypropylene thereon. Thesefabrics also produce excellent test results against hydraulic pressure.

Reasonable variation and modification are possible within the scope ofthe foregoing disclosure and the appended claims of the invention, theessence of which is that there has been set forth an impervious coverstructure which comprises a non-woven polyolefin fabric, mat or webfused externally on one side and placed with that side against a surfaceor area to be protected or rendered impervious and then covering theother side on which the surface fibers are unfused with a mix turecontaining asphalt and asbestos fibers, substantially as described.

We claim:

1. A method of providing a surface covering comprising a non-wovenpolyolefin fabric, mat or web, fused externally on one side and havingunfused fiber on the other external side, which method comprises placingsaid polyolefin fabric, mat or web, which can be needle-punched, againsta surface to be rendered impervious to fluids, the side of the fabricplaced against the surface to be covered having been fused and thencoating the other side of the fabric which presents unfused fibers witha mixture containing asphalt and asbestos fibers.

2. A method according to claim 1 wherein the fabric is polypropylenefabric made by needle punching together a mass of non-woven fibers andwherein the asphalt-asbestos mixture is cut-back with a sufficientamount of a solvent or oil to make the resultant blend applicable tosaid other external side by hot application at a temperature below thatwhich will adversely melt said polyolefin fabric, mat or web, and thecut-back asphalt-asbestos mixture is applied to said other side at therate of approximately 3-5 pounds per square yard of the fabric of theasphaltic mixture, and the mixture applied to said other side is allowedto cure in air at ambient temperature.

1. A METHOD OF PROVIDING A SURFACE COVERING COMPRISING A NON-WOVENPOLYOLEFIN FABRIC, MAT OR WEB, FUSED EXTERNALLY ON ONE SIDE AND HAVINGUNFUSED FIBER ON THE OTHER EXTERNAL SIDE, WHICH METHOD COMPRISES PLACINGSAID POLYOLEFIN FABRIC, MAT OR WEB, WHICH CAN BE NEEDLE-PUNCHED, AGAINSTA SURFACE TO BE RENDERED IMPERVIOUS TO FLUIDS, THE SIDE OF THE FABRICPLACED AGAINST THE SURFACE TO BE COVERED HAVING BEEN FUSED AND THENCOATING THE OTHER SIDE OF THE FABRIC WHICH PRESENTS UNFUSED FIBERS WITHA MIXTURE CONTAINING ASPHALT AND ASBESTOS FIBERS.
 2. A method accordingto claim 1 wherein the fabric is polypropylene fabric made by needlepunching together a mass of non-woven fibers and wherein theasphalt-asbestos mixture is cut-back with a sufficient amount of asolvent or oil to make the resultant blend applicable to said otherexternal side by hot application at a temperature below that which willadversely melt said polyolefin fabric, mat or web, and the cut-backasphalt-asbestos mixture is applied to said other side at the rate ofapproximately 3-5 pounds per square yard of the fabric of the asphalticmixture, and the mixture applied to said other side is allowed to curein air at ambient temperature.